Towards sustainability with building services systems : – by focusing on material choices, energy use and thermal indoor climates in residential buildings

Abstract: For a development to be considered sustainable, social, economic and environmental requirements must be met. The Swedish sustainable development goals, based on Agenda 2030, contain 16 national environmental quality goals. The National Board of Housing, Building and Planning is responsible for achieving the goal "A good built environment". Essential factors chosen for studies are: indoor environmental quality (IEQ) and material and energy use, as these have a major impact on the opportunities for the construction and real estate sector to achieve the goals of sustainable development. The overall aim of the thesis is to provide knowledge about how building services systems in residential buildings can contribute to sustainable development in general.The work behind the thesis consists of two parts. The first part begins with a literature review (Publication I) followed by a case study (Publication II) with life-cycle inventories and energy simulations for two multi-family buildings. Material types, quantities, manufacturing, transport and operating energies as well as the influence of material choice on the manufacturing energy were analysed. The conclusions were that only a few materials accounted for 80 % of the weight and for 80 % of the manufacturing energy in building services systems, that material choice was an important factor that influenced the manufacturing energy. Furthermore, it was found that the service life of materials and components, as well as reasons for replacements, were poorly known. As this is an uncertainty factor when carrying out life-cycle analyses it led to an interview survey (Publication III) being conducted among property management companies to increase knowledge in these fields. The reasons for carrying out replacements and the ages for components in building services systems in nine estates are analysed and categorized. The study concluded that there were multiple reasons for replacements and the deciding factor was often unclear. An attempt was made to assess the service life of some components. The assessment revealed large uncertainties, either because the data material was limited or because the reality is unpredictable. These three publications formed a licentiate dissertation, approved 2001.The second part of the thesis begins with a life-cycle cost analysis based on energy simulations and cost calculations. The profitability of a number of energy efficiency measures taken in a multi-family building was compared (Publication IV). Increased investment costs are paid for by having lower energy costs. Heat recovery with ventilation heat exchangers and exhaust air heat pumps results in about the same life-cycle cost, but an exhaust air heat pump means a greater electricity demand.A residential real estate company used a system for individual metering and billing (IMB) of space heating costs, in which the tenants paid for having a specific temperature, which meant that room temperatures were measured in all living rooms and bedrooms. In some estates a feedback control system, based on indoor temperature measurements, was introduced. The purpose of the method was to achieve more even and, on average, lower indoor temperatures, which would hopefully result in lower energy needs for heating. The feedback control was evaluated by comparing the independence of the indoor temperatures on the outdoor temperature before and after implementation (Publication V). The control method clearly indicated a lower dependency. Based on a large data set with temperature measurements during two heating seasons a comprehensive study of the indoor thermal conditions was carried out (Publication VI). The buildings in question had hydronic heating systems with feedforward control. Temperatures were almost normally distributed and seemed to vary randomly and independently of location in the building. There was a tendency for cool apartments to be cool all year-round and vice versa. Systematic variations were observed both during the day and between weekdays and weekends. Temperature variations within apartments were studied according to apartment size (Publication VII). Generally, the temperatures were lower in bedrooms than in living rooms, and the more rooms the larger the differences. Using a mathematical model of a multi-storey building, it was shown that there was a heat flow up through the building via the floor slabs (Publication VIII).During the heating season, the temperature gradients were measured in ten apartments in a three-storey multi-family building, the gradients being measured for a week in each apartment. The measured gradients were generally smaller than those calculated by the IMB system, which indicated that tenants were invoiced for lower temperatures than those actually achieved (Publication IX).An additional study was conducted in which the effects of the energy efficiency measures on the energy use in one of the buildings from a previous case study were examined and it was found that increased heat recovery increased the environmental classification grade.The various studies are discussed under the section headings Material resources, Energy use, Indoor environment quality, Laws and regulations and Sustainability concept trends. Issues such as replaceability, flexibility and user interaction are also addressed.